Up to this time, various leather products such as bags or bracelets produced by using the skin of animals like cows have been known on the market. These leather products are formed in various shapes by processing leather materials by sewing, physically folding, twisting or pressing. In addition, ornamental designs are applied on the leather products by creating grains by using these methods.
However, according to these conventional methods, the shape of the grains created on the leather skin has to be limited to man-created ones and the deformation of the leather skin created by these method is not permanent. Therefore, the ornamental effect which can be achieved by these conventional methods is limited.
Further, since it has not been possible to create a large convexity by performing a permanent deformation processing to the leather skin, the effect of creating concavity-convexity shapes to the leather skin to create an ornamental design is also limited.